The present invention relates generally to barcode scanners, and, more specifically, to light collection systems therein.
A typical laser barcode scanner is configured to scan an outbound laser beam across a barcode, and decode the inbound back scattered light therefrom. A typical one-dimensional barcode in accordance with the Universal Products Code (UPC) includes a series of alternating dark bars and white spaces of varying width for encoding data. As the laser beam scans across the barcode, light is reflected from the white spaces and absorbed by the dark spaces to modulate the back scattered light, which may then be suitably demodulated or decoded.
The laser beam is segmented into scan lines by reflection from a mirrored spinner, which scan lines are projected against the barcode either directly or upon reflection from one or more pattern mirrors. As the scan lines traverse the barcode, light is typically back scattered into a hemisphere or cone perpendicular to the barcode. In order to read the barcode, some of the scattered light must be collected by the scanner and converted into electrical energy which is suitably decoded. The inbound collection path of the scanner is typically identical in most part with the outbound scanning path but in reverse order. The spinner, therefore, not only scans the laser beam in the outbound path, but also descans the back scattered light in the inbound path, which may then be decoded.
However, since the outbound and inbound optical paths are substantially identical or coextensive, the inbound scattered light must be suitably separated from the outbound laser beam and imaged onto a photodetector for conversion into electrical energy.
The collection system for the inbound light therefore adds to the complexity and cost of the scanner. A typical collection system includes a mirror with a bypass hole therethrough which allows the outbound laser beam to pass through the hole without deviation while deflecting the inbound light to the photodetector, typically also using a focusing lens therebetween. Mirrors are relatively expensive to manufacture since they require precision light reflecting surfaces thereon. The location of the photodetector is controlled by the available location of the collection mirror which typically positions the photodetector remote from the laser in different areas and on different printed circuit (PC) boards.
Accordingly, it is desired to simplify the collection path in a barcode scanner for reducing complexity of the scanner, space requirements, and cost.